The main reason the Malock desert was feared by all was the fear of the unknown. Surprisingly people were even more afraid of the mystical desert than the black zone of the south.
The reasons for this were both distance and the cloud of mystery hovering over the red zone of the desert.
The Malock desert was closer to the 3 empires than the Black Zone. So the great distance between the southern continent and the others made people forget and not take the dangers of the southern continent seriously.
Also, unlike the joint expedition of the 3 empires that visited the black zone and came back alive, there were only a handful of people that had managed to survive the red desert. Most of them were dead, and those alive were all fugitives, so there was no one to debunk the mystery.